location bar: fix deadlock (closes #364)

Pressing escape while the location bar was focused closed the location
bar but failed to update the toolbar button state. Clicking the button
afterwards would then deadlock nemo. This fix makes sure to update the
state of the associated action group when the location bar gets hidden.

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Merge branch 'location-entry-fix' of https://github.com/nkoep/nemo